1. Field of the Invention
The present invention relates to a method and a Mobile Node, for supporting authentication of a Routing Advertisement message received directly from an Access Point.
2. Description of the Related Art
When a Mobile Node (MN) enters the domain of a new Access Point (AP), it must configure a new Internet Protocol (IP) address, usually consisting of an Internet Protocol version 6 (IPv6) address, in order to communicate with an Internet network through this AP. To achieve this, the MN needs to receive, from an Access Router (AR) linked to the AP, a Routing Advertisement (RtAdv) message comprising Network Prefixes that the MN uses to configure the new IP address. Only when the new IP address has been fully configured, the MN may start packet data communication with the Internet network.
Configuration of the IP address is a lengthy process. Firstly, though the AR sends periodic RtAdv messages, usually in Multicast fashion, it is not authorized to send such messages at a higher rate than once every three (3) seconds (RFC2461, “Neighbor Discovery for IP Version 6 (IPv6)”, T. Narten, E. Nordmark, W. Simpson, IETF, December 1998). Secondly, in order to prevent different Mobile Nodes, or other clients, from acquiring the same IP address and disrupting each others' communication, the MN must, as a part of the IP configuration process, initiate a Duplicate Address Detection (DAD) procedure. The DAD procedure introduces large delays, on the order of one (1) second, in the IP address acquisition process. Delays introduced by the low periodicity of the Routing Advertisement messages and by the DAD procedure become critical during handoff since they add an undesirable latency. This latency is especially harmful when the Mobile Node (MN) is running time sensitive applications.
The Fast Router Discovery (FRD) proposal (“Fast Router Discovery with RA Caching”, draft-jinchoi-dna-frd-00.txt, JinHyeock. Choi, Dong Yun. Shin, IETF, Jul. 12, 2004) aims to minimize the compulsory delay, as described in RFC2461, which prevents the MN from receiving a RtAdv from a new AR immediately after moving to a new link. For this purpose, the Fast Router Discovery (FRD) consists on caching a content of RtAdv message(s) in the AP. When the MN enters the domain of a given AP, it sends towards the AP an Association Request message. Because the AP has cached the content of the RtAdv messages, it then forwards this content in parallel with sending an Association Response message to the MN. This enables the MN to start the process of configuring its IP address without waiting for a periodic RtAdv.
The main threat in the above scenario consists on caching a fake RtAdv message in a malicious AP, which allows launching an easy Denial of Service (DoS) attack against the MN.
There would be clear advantages of having a method and a Mobile Node for allowing verification of the validity of a Routing Advertisement message received directly from an Access Point, in the context of Fast Router Discovery technology.